using System;

namespace ConsoleApplication
{
    class Program
    {
        static void Main(string[] args)
        {
            int A = Convert.ToInt32(Console.ReadLine());
            int curValue = 1;
            int count = 0;
            while(curValue <= A)
            {
                count++;
                int prevValue = curValue;
                curValue+= prevValue;
            }
            Console.WriteLine(curValue == A ? count : "-1");
        }
    }
}